Original owner yes, we have some plans, but not the "blue prints" plans describing where everything runs in the walls.

Sadly there isn't a phone line running in every room. (Visited the house when it was still under construction fully built just no drywall).

Edit : Problem with heating ducts is the way they are assembled, they fit into one another, so if you're going in the wrong way it's nearly impossible to get a wire to not get stuck + screws sticking out everywhere.

We were extreme lucky when we bought the house, there was a waiting time of 8 months for new houses when we were looking and turns out the previous buyer had backed out the morning off and his house was already partially done, so we took over, which means we couldn't change anything in the plans anymore (adding wires, changing room layout).